Turbine blade shrouding



Oct. 20, 1942. I J. A. RYDMARK 2,299,429

- TURBINE BLADE SHROUDING Filed March 8, 1941 11 :5 l9 l7 l9 l8 WITNESSES: i m n V ll if I INVENTOR KW I H g l J SSYEF H. RYDMRRK.

ATTORNEY Patented Oct. 20, 1942 TURBINE BLADE SHROUDING Jose! A. Rydmark, Lansdowne, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 8, 1941, Serial No. 382,323

Claims.

The invention relates to turbine blading, more particularly to blading of the impulse type used in the high-pressure region of a turbine and subject to rapid temperature changes, and it has for an object to provide shrouded blades connected by anelastic member.

A more particular object of the invention is to tie together blades having dependent shroudforming elements by means of an elastic member.

A further object of the invention is to provide a metallic member for connecting together a plurality of shrouded turbine blades, the member being yieldable circumferentially of the blade row and relatively rigid in a direction transverse thereof.

These and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the acocmpanying drawing forming a part of this application, in which:

Fig. 1 is a side elevation, partly in section, showing the improved elastic member attached to the turbine blades;

Fig. 2 is a top plan view showing the improved elastic member;

Fig. 3 is a sectional view taken along line III-III of Fig. 2; and,

Fig. 4 shows a modified way of attaching the elastic member to the blades.

Referring now to the drawing, the blades III are of the conventional impulse type and each is provided with its individual shroud-forming element II. With an assembly of blades, the shroud-forming elements II are juxtaposed to form shrouds constituting the outer boundary walls of the blade passages; and the present invention makes it unnecessary to connect the shroud-forming elements together. Instead of such a connection, there is provided an elastic band, at I2, disposed outwardly of the shroudforming elements and attached to the respective blades.

The metallic elastic band comprises portions I3 for the respective blades and which are elongated transversely of the blade row. The elongated portions I3 are joined by connecting members I4 arranged alternately with respect thereto, each connecting member having circumferentially-extending portions I5 integral with the ends thereof and extending in oposite directions, one circumferentially-extending portion being integral with one adjacent elongated member I3 and the other circumferentially-extending portion I5 being integral with the other adjacent elongated member I3. This arrangement provides a structure which is yieldable or elastic in a circumferential direction and which is relatively stiif in a direction transverse to the blade row.

The elongated members are provided with openings to receive means by which such members may be fastened to the respective blades. Preferably, as shown in Figs. 2 and 3, the elongated members I3 have openings Il to receive tenons I8 having heads I9 formed to overlap the outer surface of the elastic band to hold the latter assembled with respect to the blade row.

The elastic band, at I2, acts somewhat as a flat spring. Preferably, it is made of suitable sheet steel cut as illustrated. By varying the thickness of the metal material or by varying the distance between the cuts, flexibility of the band can be varied. As temperature stresses are eliminated, the improved type of shroud strip or band may be arranged to connect together a larger number of blades in a group. Furthermore, as the elastic band can be calculated for a given flexibility with a high degree of accuracy, it can be used to advantage to raise the frequency of blades a desired amount.

The shroud band also has the advantage of serving as a damping device for blades, if the heavy or transversely-elongated portions I3 are arranged to provide for angular movement relative the blade pins or tenons. Accordingly, in Fig. 4 there is shown an arrangement wherein screws 20 attach the elongated portions I3 to the blades, the screws having tapered heads 2| for engagement in tapered openings 22 formed in the elongated portions I3. Centrifugal force acting on the elastic shroud would tend to urge the latter outwardly against the taper of the screw heads with the result that friction would thereby be made available for the absorption of vibration energy.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and it is desired, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What is claimed is:

1. In a turbine, a row of blades, each blade having a shroud-forming portion and the shroudforming portion providing outer boundaries for the blade passages between blades, said blades having tenons extending outwardly from the shroud-forming portions, an elastic metallic band for connecting the tenons together, said elastic metallic band comprising members elongated transversely of the blade row and connected to the tenons and members arranged alternately with respect to the elongated members for connecting the latter together, said connecting members being relatively still in a direction transverse to the blade row and yieldable circumferentially thereof.

2. In a turbine, a row of shrouded blades, an elastic shroud band comprising elongated members for the respective blades and connecting members integral with the elongated. members and arranged alternately with respect thereto, each connecting member including a portion ex- ,tending between adjacent elongated members and having one end joined. by a circumferentially-extending portion to one of they adjacent.

elongated members and having its other end joined by, a circumferentially-extending portion tothe other of the adjacent elongated members, and:means1 for connecting the elongated mem:- here to; the respective blades.

3. The combination as claimed in claim 2 wherein the means for connectingthe elongated members to, the respectivepbladfis comprises inrwardlyetapered openings formedin the elongated membersand pinsconnected to the blades andhaving inwardly-tapering head portions cooperating with the openings.

4. In a turbine, a row of shrouded blades, an elastic shroud band comprising members for the respective blades and; elongated in a direction transverse to the blade row and connecting membersintegral with the elongated members and arranged alternately with respect to the latter; each connecting member including a portion extending between and parallel to adjacent elongated members and having one end joined by a circumferentially-extending portion to one of the adjacent elongated members and having its other end joined by a circumferentially-extending portion to the other of the adjacent elongated members; said elongated members having openings formed therein; and pin elements carried by the respective blades, extending through said openings and having heads arranged in overlapping relation with respect to said elongated members.

5; In a turbine, a row of shrouded blades, each blade having a shroud-forming element, an elastic shroud band disposed outwardly of the shroud-forming elements, said elastic shroud comprising members for the respective blades and elongated transversely of the blade row and connecting members'integral with the elongated members and arranged alternately Wlth' respect thereto, each connecting member including a portion extending between adjacent elongated members and having one end joined by circumferentially-extending portions to one of a pair of adjacent elongated members and having its outer end joined by circumferentially-extending portions to the other adjacent elongated member, said elongated members having openings therein and engaging said shroud-forming elements of the blades, and means for connecting the elongated members to the blades and including pins arranged in the openings and attached to theblades.

JOSEF'A- RYD ARK- 

